In correspondence with the increasing requirement for variety and properiety of information, multiple information service systems have been developed in many countries which can provide various information such as picture image or data through a wideband large-capacity communication network. For such systems, there has been considered the multipurpose utilization of fundamental media such as broadcasting waves or telephone network. As regards the utilization of broadcasting waves, in addition to the experimental character multiplexed broadcasting in Great Britain called "TELETEXT", development tests are new effected in many countries on audio multiplexed broadcasting and on character multiplexed broadcasting. On the other hand, as regards the utilization of telephone network, development tests called "PRESS-TEL" have been exercised by the British Post Office and have gained public favor.
The present invention relates to multiple information service systems in which the telephone communication and the TV broadcasting, each being one of fundamental media of nation-wide scale, are combined into one and which can provide various information such as picture image or data.
As the approach to multipurpose utilization of broadcasting, telephone and the like, there can be considered the following manners: (1) effective utilization of the existing communication networks, (2) development of regional small-scale systems for the public, and (3) prevalence of individual private systems. As examples effectively utilizing the existing communication networks, there are known such systems in Great Britain as called CEEFAX or PRESS-TEL (VIEWDATA), which employ effectively the existing communication media such as broadcasting waves or telephone network. As the regional small-scale systems for the public, PYRAMID system of Ampex Corp. and "Interactive Cable Vision" of Mitre Corp. have been tested in U.S.A.
However, the above-mentioned PRESS-TEL system in Great Britain is such that the information requested through a telephone circuit from a terminal is data-transmitted to the terminal again through the telephone circuit go display a desired picture image on a terminal color TV receiver or a special display device having display and telephone functions. In this system, character codes and picture element indicating codes which employ a part of the character codes are transmitted from the center to a terminal to form and display one picture image by means of a character generator provided in the terminal. Therefore, this system has drawbacks that it is impossible to transmit any stationary picture and that the terminal inevitably becomes expensive. Incidentally, the ANTIOPE system, which has been put into practical use in France, is the same kind as the above-mentioned PRESS-TEL system.
Further, in the PYRAMID system developed by Ampex Corp. for a video/audio information searching system in school, respective information from a video information source such as a TV camera provided in the center and from an audio information source such as a microphone is at once stored in video and audio masters. In response to a request from a terminal, video and audio signals for one frame, which are randomly picked up from the above masters, are first transferred to video and audio buffer memories and then transmitted to the terminal. However, because of a lack of exchange function on the center side, this system has drawbacks that it is wanting in expansibility, that its utilization is limited to a narrow region and that the center is expensive when viewed from the terminal.
Further, one of two kinds of TICCIT system developed by MITRE Corp. is for a very narrow region such as school and the other is for a small area covering about 2000 terminals. Each system operates as follows. In response to a request from a terminal, digital character signals are outputted from a character generator controlled by a computer, and the signals for one frame are at once stored in a refresh memory. The stored signals are transformed into video signals through the repeating regeneration and are transmitted, after the modulation by a modulator, to a plurality of terminals through a single coaxial cable. However, it is impossible for the system to produce analog half-tone since the digital character signals are formed and used. Further, the system is great in division loss and is wanting in expansibility and in effect due to large grouping, since it has no exchange function. Although, in view of the above-mentioned, a hub system is used, the cost of the center side viewed from terminals is as high as in the PYRAMID system. Further, the system is small in expansibility as compared with systems utilizing the existing public circuit, since the video information and the audio information are transmitted through respective transmission lines.